Ladies and gentlemen,
I found some odd behaviour when using trace-cmd together with trace_marker.
I try to use trace-cmd to trace scheduling events to find out latencies on my box.
trace-cmd record -e 'sched_wakeup*' -e sched_switch
In oder to synchronize the trace I use echoing to /sys/kernel/debug/tracing/trace_marker
echo Hallo > /sys/kernel/debug/tracing/trace_marker
This works fine so far.
My task in observation is set to run only on one core (on a quad core cpu)
so I tried to narrow down the focus of tracing (and the data amount) using the -M option:
trace-cmd record -M 2 -e 'sched_wakeup*' -e sched_switch
But from this point on I am no longer able to write to the trace_marker, instead I get this response:
bash: echo: write error: Bad file descriptor
Only reboot solves the problem.
Is this some known or even intended behaviour? Or do I use it in some weird way as described?
Maybe I understood something wrong and you can give me a hint how to overcome the obstacle.
Thanks a lot
Juergen
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